Serum has been known to stimulate collagen production by dermal fibroblasts
. As part of an ongoing study of the molecular mechanisms of collagen produ
ction, we have investigated transcriptional regulation of the human alpha2(
I) collagen gene by serum in human dermal fibroblasts. Serum responsive ele
ments were mapped by deletion analysis between by -353 and -264, and betwee
n -148 and -108 in the alpha2(I) collagen promoter. Further functional anal
ysis of the alpha2(I) collagen promoter containing various substitution mut
ations revealed that serum stimulation of this promoter is mediated equally
by a GC-rich region located between by -303 and -271 and by the TCCTCC mot
if located between by -123 and -128, both of which constitute binding sites
for transcription factor Sp1 and Sp3. No differences were observed in elec
trophoretic mobility shift assays between unstimulated and serum stimulated
fibroblasts. The Sp1 inhibitor mithramycin blocked stimulation of the alph
a2(I) collagen promoter activity by serum. Furthermore, immunoprecipitation
analysis showed that serum stimulation increased Sp1 phosphorylation. In c
onclusion, this study characterized response elements that mediate serum st
imulation of the human alpha2(I) collagen promoter and suggests that serum
stimulation was mediated via Sp1/Sp3 binding sites in this promoter.